title: Reversible and competitive inhibitory kinetics of amoxicillin on mushroom tyrosinase.
abstract: In the present work, we investigated the inhibitory effects of amoxicillin, a bacteriolytic β-lactam antibiotic drug, on the rate of monophenol hydroxylation and o-diphenol oxidation catalyzed by mushroom tyrosinase. The results showed that amoxicillin could inhibit both monophenolase and diphenolase activities. For monophenolase activity, the inhibition on reaction rate was dose-dependent, while the influence on lag period was not obvious. For diphenolase activity, amoxicillin was found to be a reversible inhibitor, with an IC50 value of 9.0 ± 1.8 mM. Kinetics analysis showed that amoxicillin was a mixed type inhibitor of the enzyme with KI and KIS values of 8.30 mM and 44.79 mM, respectively. Further, the molecular mechanism underlying the inhibition of tyrosinse by amoxicillin was investigated by means of fluorescence quenching and molecular docking techniques. The results showed that amoxicillin could form static interaction with the catalytic pocket of the enzyme through the interaction of amoxicillin with the dicopper irons and amino acid residues in the enzyme active center. Our results contributed to the usage of amoxicillin as a potential tyrosinase inhibitor in the field of medicinal industry and could also provide guidance in the design of novel tyrosinase inhibitors.
authors.affiliation: Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, School of Life Sciences, Xiamen University, Xiamen 361005, China.
authors.forename: Xiao-Xin
authors.initials: XX
authors.lastname: Chen
authors.forename: Jian
authors.initials: J
authors.lastname: Zhang
authors.forename: Wei-Ming
authors.initials: WM
authors.lastname: Chai
authors.forename: Hui-Ling
authors.initials: HL
authors.lastname: Feng
authors.forename: Zhi-Hao
authors.initials: ZH
authors.lastname: Xiang
authors.forename: Dong-Yan
authors.initials: DY
authors.lastname: Shen
authors.forename: Qing-Xi
authors.initials: QX
authors.lastname: Chen
mesh_terms: D000363:Agaricales / Q000201:enzymology*; D000658:Amoxicillin / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D001665:Binding Sites; D001667:Binding, Competitive; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D007700:Kinetics; D007980:Levodopa / Q000378:metabolism; D008958:Models, Molecular; D008968:Molecular Conformation; D062105:Molecular Docking Simulation; D014442:Monophenol Monooxygenase / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D019906:Nuclear Magnetic Resonance, Biomolecular; D010084:Oxidation-Reduction / Q000187:drug effects; D010088:Oxidoreductases / Q000037:antagonists & inhibitors; D011485:Protein Binding
chemical_list: D004791:Enzyme Inhibitors; D007980:Levodopa; D000658:Amoxicillin; D010088:Oxidoreductases; C412191:monophenolase; D014442:Monophenol Monooxygenase
keywords: Amoxicillin; DMSO; Fluorescence quenching; IC50; K(I); K(IS); Molecular docking; Molecular mechanism; Mushroom tyrosinase; dimethyl sulfoxide; equilibrium constant of the inhibitor combining with the enzyme–substrate complex; equilibrium constant of the inhibitor combining with the free enzyme; l-3,4-dihydroxyphenylalanine; l-DOPA; l-Tyr; l-tyrosine; the inhibitor concentrations leading to 50% activity lost